For the second time, Prince George's County Police Lt. Richard Welsh gave a polite ultimatum to the abortion protesters blocking the entrance of a Greenbelt clinic yesterday morning: "Move," he said, "or we'll have to arrest you for trespassing."

In answer, the 28 representatives of the antiabortion Non-Violent Action Project inched closer to the doorway of the Metropolitan Family Clinic at 5915 Greenbelt Rd. They linked arms even tighter to form a human chain and gazed resolutely at the street beyond.

"What about the murder that is taking place inside?" asked Harry Hand, 27, a coordinator for the Gaithersburg-based group. "What about the violation of that law?"

"I'm not here to debate the issue with you," Welsh said impassively.

And the arrests began; an organized assembly line that started when the officers bent down to ask each individual if he or she would leave voluntarily and ended with four paddy wagons filled with the 28 handcuffed protesters.

In between, police officers had to drag the demonstrators to the waiting wagons, after first prying their fingers from around door posts. Suzanne Mattina, a legal secretary from Mount Rainier who joked about her weight, went limp as the officers carried her from the doorway. Later she lay stretched on her back on the pavement while police helped another protester into the van.

"I'm very comfortable," she said, looking up into a ring of reporters and photographers. "I'm very happy. Let them pick up my dead weight." The officers complied.

The demonstration reflected a strategy that goes beyond routine picketing of an abortion clinic -- although the doorway protesters were accompanied by a group of about 40 adults and children who marched solemnly up and down the sidewalk with signs.

Ideally, the antiabortionists had hoped not only to block the entrance of the clinic, but also to place special "counselors" in the waiting rooms to talk to women about possible alternatives to abortion, Hand said.

But when the caravan arrived at the clinic, the door was locked and the demonstrators had to modify their plan. Police said, however, that the clinic staff and six female patients were inside.

Margaret Murphy-Molloy, an Olney housewife who spent two nights in jail in January as a result of a similar protest outside a Wheaton clinic, managed to get into the Greenbelt facility -- but only for a moment before the staff escorted her outside.

The demonstration was the first in Prince George's County that resulted in arrests, police spokesman Bruce Gentile said. By midafternoon, all 28 protesters had been released on personal recognizance after appearing before a court commissioner in Hyattsville. The charge, trespassing, carries a maximum $500 fine, Lt. Donald Studds said.

At one point during the protest, a young woman with long brown hair walked up to the clinic entrance and tried to get past the human wall, but she was turned away by an employe who cracked the door open slightly to talk to her.

"No," the woman said to the protesters' pleas that she stay and talk with them. "Why I am here is my business."